Oops! She did it again.

Things got a little bit awkward during Britney Spears' Las Vegas residency when she appeared to be lip synching to Sia during a recent performance.

As Britney strutted her stuff onstage, she held the mic in her hands and seemed like she was singing her hit 'Perfume' -- only it was Sia's vocals that were heard in the venue. Yikes!

Of course, the incident isn't too mind-blowing -- after all, Sia co-wrote and sang backing vocals on the track, and Britney's manager even confirmed that the pop superstar doesn't sing the whole time throughout her 'Piece of Me' set.

"To put on the show that she puts on, it’s virtually impossible to sing the entire time and do what she does,” he revealed in a Medium interview. “She’s singing on every song, basically, when she has the ability to sing. There’s no way you can dance for 90 minutes straight and sing the entire time.”

Back in February, the singer was accused of lip syncing to her track 'Alien.' Britney Spears lip syncing to Sia might not be entirely shocking -- but we have to admit, it's pretty freaking awkward.

Check out Britney Spears' performance of 'Perfume' in the video above.

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